Olefin polymers formed by the polymerization of olefin monomers in the presence of a Ziegler-Natta catalyst have a high degree of crystallinity and beneficial physical properties which make them particularly useful in the production of molded articles, films and fibers. Ziegler-Natta catalysts are formed by the reaction of an inorganic compound of a metal of Groups IV-VIII of the Periodic Table, such as titanium metal tetrahalide. Olefin polymers which are both stereoregular and sterospecific are formed by the polymerization of olefin monomers in the presence of certain Ziegler-Natta type catalysts. Typically the crystallinity is from about 20 to about 90% as determined by X-ray diffraction.
Notwithstanding the very desirable and beneficial properties of these olefin polymers, they are quite susceptible to degradation due to prolonged exposure to sunlight or other sources of ultraviolet radiation. Hence, a number of stabilizers have been developed over the years which tend to inhibit the degradation of these olefin polymers. However, these stabilizers suffer from one or more deficiencies. For example, they have an adverse effect on the physical properties of the olefin polymers during processing, or they fail to provide a product which has any appreciable storage stability due to limited compatibility with olefin polymers.
U.S. Pat. No. 4,233,410 describes oligomeric or polymeric polyalkylpiperidine derivatives manufactured by a poly-condensation reaction or polyaddition reaction as polymeric light stabilizers. The polymeric light stabilizers have an average degree of polymerization of 2 to 50 and a molecular weight of up to 10,000, polymers having an average molecular weight of from 1,000 to 6,500 are exemplified.
Polymers and copolymers of an unsaturated carboxylic acid ester containing at least one 2,2,6,6-tetraalkyl piperidyl group in the molecule or a copolymer of said unsaturated carboxylic acid ester with another copolymerizable unsaturated monomer containing a 2,2,6,6-tetraalkyl piperidyl group having a molecular weight of 1,000 to 20,000 as polymeric light stabilizers are disclosed in EP 65655.
U.S. Pat. Nos. 4,775,496 and 4,946,879 describe antidegradants for rubber compounds consisting of the reaction product of a rosin acid and a polyfunctional compound having at least one functional group capable of reaction with a carboxylic acid functionality and another functional group having antidegradant properties selected from the group consisting of 4-hydromethyl-2,6-di-t-butylphenol, 4,4'-methylenebis-(2,6-di-t-butylphenol), 4,4'-butylidenebis-(6,-t-butyl-3-methylphenol), 4,4'-thiobis(6-6-butyl-m-cresol), 4,4'-thiobis(6-t-butyl-o-cresol), 2-mercaptobenzimidazole, p-amino-diphenylamime, p-hydroxy-diphenylamine, p-hydroxy-p'-amine-diphenylamine and p,p'-diamino-diphenylamine.